Ottersen was a
research fellow at the Institute of Anatomy at the University of Oslo from 1978 to 1983 and a
prosector (which in Norway is an academic rank in anatomy equal to
reader) at the same institute from 1983 to 1992. He was promoted to professor in 1992. He has been head of department of the Institute of Anatomy (1997–1999), Pro-Dean for Research of the Faculty of Medicine (2000–2002) and director of the Centre for Molecular Biology and Neuroscience at the University of Oslo (2002–2009), a centre of excellence funded by the
Research Council of Norway. He was editor-in-chief of the journal
Neuroscience 2006–2009.
Rector of the University of Oslo In 2009, he was elected as the
rector of the University of Oslo, while
Inga Bostad was elected as the pro-rector. At the University of Oslo the rector is directly elected to a four-year term by all employees and students, and may serve a maximum of two terms; the rector is the university's ceremonial head, chief executive officer and chairman of the board and thus corresponds to both the chancellor and the vice chancellor at a British university. By convention and formerly also by law, the rector is elected among the professors at the university. The rector's deputy and the university's second highest official, the pro-rector, is also directly elected alongside the rector. In 2013, he was re-elected for a second term, while
Ruth Vatvedt Fjeld was elected as the new Pro-Rector; she resigned the following year and was succeeded by
Ragnhild Hennum. Ottersen became a board member of
Oslo University Hospital in 2011 and became chairman of the board of the Norwegian Association of Higher Education Institutions in 2013. He attended the
Bilderberg Group meeting in 2011.
Rector of Karolinska Institute On 20 February 2017 the board of the
Karolinska Institute in Sweden nominated Ottersen to become rector of Karolinska Institute. He was formally appointed as rector by the Government of Sweden on 27 April 2017 and assumed the position on 1 August 2017. In 2019 Ottersen became a member of the
Lancet–SIGHT Commission on Peaceful Societies Through Health and Gender Equality, chaired by
Tarja Halonen. ==Research==